input the number of seconds to record (400 for the Flash version, 180 for the HTML5 version)

input the file name to record to (make sure to name it something.wav)

Whatever method you decided to use (Audacity or virtual audio device), enable recording NOW by clicking the record button in Audacity, or click the “Open” button in the file selection prompt of virtual audio device.
In the latter case, please wait for cmd.exe to indicate that ffmpeg has started and is recording.

Then

start playback in your browser

wait for the playback to finish

In case you're using virtual audio device, carry out these additional steps (ignore for Audacity):

WAIT for a file explorer window to pop up

open something.wav with Audacity

Once you've got the sample, follow these steps:

delete the silence before and after the recording (select, press the delete key)